So long as your knees don't give up on you, you are still young. So long as you can still put a needle through a thread...you are still young. As long as you don't need help getting up (or down), you are still young. And if you are 75 and with good knees, then you are still young...BUT we are all different. I felt old at 13 but feel young and I'm 34 now. Life was much harder then and now I'm more scared so I feel like Benjamin Button.